We investigate in-service teachers' scientific engagement in a blended online science inquiry course. We analyze a shift from teachers following instructions to doing science themselves, and we characterize it at two levels: first, in how teachers engaged in individual sense-making; and second, in how they oriented to the online community as a space for collaboration and collective knowledge building. This progress, we show, was made possible by a shift in how the teachers "framed" the course--how they understood and interpreted the purpose of the activities--a shift that entailed both epistemological and affective dynamics. This shift in framing was supported by the instructors' efforts to attend to and address participants' epistemology and affect, both in face-to-face and in online interactions. A key implication of this study is the importance of instructional attention to epistemology and affect to create online learning environments that promote productive framings of scientific inquiry.